Stabilizers are often used in polymeric compositions, e.g., polyolefins, polyvinyl halides, polyesters, polyamides, nitrile polymers, styrenic polymers and acrylate polymers and elastomeric materials such as butadiene rubber, polyisoprene etc to stabilize the polymeric compositions against the effects of heat and light degradation. Exemplary of such stabilizers are phenolic antioxidants, hindered amine light stabilizers, ultraviolet light absorbers, phosphite antioxidants, metal salts of fatty acids, hydrotalcites, metal oxides, epoxidized oils, hydroxylamines, amine oxides, lactones, and thiosynergists. In particular, organic phosphites have been used as antioxidants, e.g., secondary antioxidants, for polyolefins, polyvinyl chloride, and elastomers. Examples of such phosphites are disclosed in H. Zweifel (Ed) Plastics Additives Handbook, 5th edition, Hanser Publishers, Munich 2000. Phosphite stabilizers, both liquid and solid, are known in the art. Many of the most effective organic phosphites are solids at ambient temperature and, accordingly, do not lend themselves to being readily combined with certain polymeric resins. As such, these organic phosphites must be processed, e.g., heated or melted, in order to be incorporated into the respective polymer compositions. Alternatively, a solid phosphite may be mixed with a liquid phosphite to thus make a liquid composition. One of the most widely used solid organic phosphites is tris(2,4-di-t-butylphenyl) phosphite, which is commercially sold under the trade names Alkanox™ 240 (Chemtura Corporation, Middlebury, Conn., USA), Irgafos™ 168 (Ciba Specialty Chemicals Corporation, Tarrytown, N.Y., USA), or Doverphos™ S-480 (Dover Chemical Corp, Dover, Ohio, USA). Tris(2,4-di-t-butylphenyl)phosphite has processability and solubility limitations, however, due to its solid form. Examples of other solid phosphites include bis(2,4-di-tert-butylphenyl)pentaerythritol diphosphite, which is commercial sold under the trade name Ultranox™ 626 (Chemtura Corporation, Middlebury, Conn., USA).
Liquid phosphite antioxidants typically do not have the processability and solubility concerns that are associated with solid phosphites. There are several different liquid phosphites, including tris(nonylphenyl) phosphite (TNPP), bis(decyl)pentaerythritol diphosphite, tris(dipropyleneglycol)phosphite, 4,4′-isopropylidenebis(didodecyl phenyl phosphite), dilaurylphenylphosphite and trilaurylphosphite (TLP). However, TNPP is widely used with most polymeric resins, especially polyolefins. Due to alleged estrogenicity concerns associated with nonylphenol, which may be present in low concentrations in some commercially available TNPP products, there is a strong desire in the art to replace TNPP with other liquid phosphites that are effective stabilizers, but which do not present such estrogenicity concerns.
Thus, the need exists for safe and effective phosphite stabilizers, that can effectively stabilize polymer resins and compositions against heat and light degradation and that are liquid at ambient conditions.